Conversion of starchy polysaccharides



Patented Oct. 4, 1938..

George V. Caesar, New York,'N. Y., assi'gnor Stein, Hall & Company, Inc., New York, N. Y.,'

a corporation of New York Serial No. 98,071

- plication August 2c, 1936, I

12 Claims. (01. 12-1-33) This invention relates to new and useful compositions of matter obtainable from starchy polysaccharides, and to a new and improved method of converting starchy polysaccharides.

5 A number of processes are known for the conversion or degeneration of starch into so-called soluble forms,,such as dextrins, thin-boiling and soluble starches. According to most of these methods starch is treated either in the dry form or in aqueous suspension with'an acid or with an.

oxidizing agent, and variously heated. The term "conversion generallyrefers to dry treatments.

Various processes have also been proposed which involve heating starchwith a strongly alkaline substance in'one form or another to produce products of a higher order of viscosity than obtained by roasting with or without pretreatments with aqueous acid.

In the various methods of treating starch, urea has been mentioned as an auxiliary gelatinizing.

agent, or as a substance adapted to lower the temperature at which starch is converted into a gelatinized material. Thus, Hoppler et al., U. S. Patent No. 1,878,852, produces swelling starches by heating thin layers of starch containing the normal proportions of water for a short period'between two faces of any desired form, at temperatures above 100 C., and simultaneously applying to the same mechanical pressure of about 2500 kg./cm. The use of urea as a substance adapted to lower the temperature at which starch is converted into starch glue is incidentally mentioned, but no proportions are given and it is apparent that the method described involves principally three factors, name- 1y, pressure, heat, and duration of the heat treatment. It produces primarily a gelatinized' starch in which the original granular organization is destroyed, asin the various hot-rolled 40 starches.

Bauer, U. S. Patent No. 1,969,347, relates to the treatment of flour by adding thereto a gel inhibiting agent, preferably a sulphite salt, and then converting the starch present. The gel inhibiting agent reacts with the small amount of gluten or other protein substance present in the flour, and thereby prevents the formation of 55 2,023,973, describes the use of urea in conjuncby the user. spect to degenerated starches, such as dextrins,

' etc., and the starch in the dry blend, as marketed,

' is wholly unaltered. Furthermore, the prepara- 10 tion with oxidizing agents, such as barium peroxide, in the treatment of starch. This treatment preferably involves the blending of a dry glue base by mixing together a starch, urea, an oxidizing agent, and a filler, and thetreatment of this glue base with water and a caustic alkali No claims are advanced with retion of the glue by the user involves the use of 'an alkali, and in this respect is analogous to other methods of treating starch with an alkali.

It is an object of the present invention to produce a new and improved amylaceous composi- 15 is relatively very high, its consistency being more analogous to that of an unconverted starch than that of a' British gum dextrin. Anotherv ob- 25 v -ject is to produce a dry material which disperses in waterand behaves generally in a manner similar to natural. gums, such as, for example, gum karaya and gum shiraz. vA further object is to produce anew and improved com- 30 position which has a wide variety of uses, and

especially in the field of natural gums, textilev color=printing pastes, asan adhesive, as a thickener or carrier for other gums, and in impregnating, coating and sizing fibrous sheet ma- 35 terials, for example, paper, cloth and the like. A still further object is theprovision of a new and improved process for producing compositions of thecharacter above described. Other objects will appear hereinafter. a 40 In accordance with this invention I have found that a new and useful composition of matter which is dispersible in water. at moderate temperatures, may be obtained by the conversion of a starchy polysaccharide with a suitable amide, 45 such as carbamide, commonly known as urea.

Inpracticing the invention I prefer to heat the starch in its natural air-dry condition to a temperatureat which .all, or nearly all, ofthe original moisture present has been removed, then to add urea and continue the heating. In this manner a conversion of the starch occurs, bu'tthe normal degeneration or hydrolytic scission, characteristic of -other types of conversion, is shown by chemical tests to be reduced. The granules g to eighteen (18) of the converted product retain their original form, but may have undergone an incipient proces of structural reorganization promoting swelling or hydration in aqueous suspension. The 6 resultant gum will disperse to an exceptionally heavy body in water at relatively low temperatures, with little or none of the normal granular disorganization which is so characteristic of the various so-called dextrin solutions. l The term "soluble" as applied to starch and dextrins is somewhat misleading, because a starch or dextrin properly possesses no true solubility,-

but only a varying degree of dispersion in aqueous suspension. The composition of my invention is soluble in the sense that it readily disperses in water to give a transparent or translucent dispersion; but unlike an ordinary dextrin of similar dispersibility, the body or viscosity of its liquid suspension is relatively high, its consis- 2'0 tency,being more analogous to that of an unconverted starch than that of a dextrin. In this respect my product-resembles a British gum or roasted dextrin having a viscosity of the order of a starch. Unlike many of the so-called soluble g5 starches, however, it will disperse in aqueous sus- Example I .40 Eighteen (18) pounds of tapioca flour were placed in a suitable converter and heated. At a temperature of 132 C., 408- grams of carbamide (urea) were added and the conversion carried to a temperature of 193 C. over'a total period of four hours.

The product wasremoved from the converter and found to be readily hydrated in cool water to produce a dispersion of relatively high viscosity which did not very markedly tend to increase in consistency, upon standing, nor after having been cooked and cooled. This product was substantially free from urea. Comparative tests showed that it possessed markedly diflerent propand the usual type of soluble roasted dextrin '(British gum).

had a creamy. or light brown color. It readily dispersed in water without heating to give a;

' ural gum. Its dispersions, e.g., one part of solid to 8-8 parts of water, were much more viscous thanthe dispersions made with the same amount of the ordinarysoluble roasted dextrin (British gum). As compared with hot-rolled starch dispersions, it also showed a much higher viscosity at high temperaturs, and a diil'erent consistency ,at all temperatures, for the same amount dispersed. Its disperslons'we're short and soft, not

stringy and sticky like the hot-rolled starch dispersions. Moreover, it gave no substantial gran- 11hr disorganization as in the case of hot-rolled fitarohesand ordinaryBritish gums. Example 11 pounds of tapioca flour were erties -from ground tapioca, hot-rolled tapioca,'

In the dry powdered state, it,

homogeneous translucent gum resembling a nat- '-at a temperature between 130 Grand 160 C. to

fifty-minutes, with results resembling Example I. 5

Example III Example I was repeated with sago flour instead of tapioca flour, the proportions and conditions .being the same otherwise. Similar results were obtained.

' Similarly, the invention is applicable to the treatment of other starchy polysaccharides. As further examples of specific carbohydrates may be mentioned wheat, rye, barley, oat, rice, maize 15 and potato starches, and sago and cassava flours. In general, especially good results have been obtained withstarches and flours substantially free from proteins. r

The amount of moisture initially present in, the starchy polysaccharide'may vary within relatively widelimits. Good results have been obtained by using starch in its normal air-dry condition, e. g.; containing approximately 10% to 20% moisture. tened starch maybe used, for example, starch containing more than about 20% of moisture but insuflicient amounts to cause gelatinization upon heating. If desired, the starchy material may be given a preliminary spraying treatment with an acid after the normal fashion, to be followed later by the addition of urea, to obtain results intermediate between normal products and' those which are typical of straight urea conversions.

The amount of urea is subject to variation, depending particularly upon the type of material treated and the results desired. In general, it is preferable to employ about 2% to 5% of urea on the basis of the natural air-dry weight of the starch. However, more or somewhat less urea may be employed.

The temperature of conversion may vary within relatively wide limits. Thus, the temperature at which active conversion takes place may vary within the range of about 130 C. to about 200 C. Normally, good results are obtained by carrying out the reaction at temperatures below 200 C. The'time of heating may vary, depending upon such factors as the raw material treated and the results desired. v

The process may be carried out at atmospheric pressure. However, lower or higher pressures may be used if desired.

The urea may be added to the starchy polysaccharide before the. starch has been subjected to heat, that is, at the beginning of the conversion. Addition of' the urea at an intermediate stage of the conversion tends to reduce the amount of tailings.

While the invention is not limited to any theory, it is believed that the useful results obtainable by the presence of urea in the treatment of a starchy polysaccharide as herein described may be explained on the following basis: Urea melts and decomposes under ordinary pressures ammonia, ammonium cyanate, and biuret, the cyanate subliming. Between and C. increasing amounts'of biuret, as well as cyanuric acid and ammelide are formed; above 190 C 70 the biuret decomposes, yielding cyanuric acid, ammelide, and tricyanourea. Above 200 C.'urea is said to decompose to ammonia, cyanuric acid, tricyanourea, and ammelide; but for the majority of dextrin conversions the process will termi- .15

However, if desired, pre-moisv arenas what between a minimum temperature suflicient 'for conversion and the temperature at which substantial charring occurs. In the conversion representative of my process, the starch granules may become coated with melted urea; and so the ammonia, which is given on abundantly, is generated directly on the granules-In situ as it were-in a manner most effective to prevent active hydrolysis with consequent scission or de-' generation, an effect invariably accompanied by great loss in the body. or consistency of the subsequently formed liquid gum. It is this release of ammonia gas intimately throughout the mass of the charge which may account for the unusual eflfect of ureajn preventing structural degeneration and loss of viscosity or body.

As a further explanation it is believed that the molten urea may induce an incipient swelling or enlargement of the granule with consequent structural dispersion which should conceivably promote subsequent hydration and so account for the useful property of easy and rapid dispersion possessed by compositions of my invention in water at relatively low temperatures.

The composition of my invention is conmierciallyuseful in: (1) The field of so-called natural gums, e. g., gum shiraz, and the like; -(2 for textile color-printing gums and pastes; (3) as an adhesive, and particularly in the field of paper adhesives; (4) as a thickener or carrier for other products, e. g., ful1ers earth, bentonite, starch, starchmixtures with formaldehyde, caustic alkalis, and/or borax; (5) as a paper beater size for certain types of paper and paper board; and (6) generally, inimpregnatlng, sizing, coating,

filling and gluing fibrous sheet materials, for ex- 7 ample, paper, paper board, cloth, and similar materials.

It will be understood that auxiliary agents may be added to my compositions for various pur' poses. Thus, I-may add oxidizing and reducing agents, e. g., sodium perborate, sodium bisulflte, sodium hydrosulflte, sodium formaldehyde sulfoxalate, and similarcompounds.

The advantages of the invention will be sip--v parent. I have found that by heating a starchy polysaccharide with urea in suflicient amounts at temperatures above its melting and decomposing point, it is possible to produce an amylaceous substance dispersible inwater at relatively low temperatures and having other new and useful characteristics: Furthermore, it is possible to convert the starohyp lysaccharide with urea by-my process without the necessity for high pressures. Additionally, my product difl'ers generally from the products obtained by the processes heretotoredescribed in that it is essentially a type of polysaccharide product commercially known as a British gum, formed by roasting, but having special physical and chemical properties, as previously noted. p s v Having thus described the invention, what I claim asnew and desire to by Letters Patent of the United-States is:

1. The process-which consists in heating a starchy polysaccharide with urea at a tempera ture of at. least the melting point ot urea in a substantially drystate 'under substantially atmospheric pressures until a product dispersible in water at ordinary temperatures is obtained.

2. The process which consists in reacting to gether starch and molten urea in a' substantially dry state under. substantially atmospheric pressures until a product dispersible in water at ordinary temperatures is obtained.

3. The process which consists in heating a normally air-dry starchy polysaccha'ride' to a temperature suflicient to remove most of the moisture present therein, adding urea'and heating the resultant mixture to a temperature above the decomposition point of urea under substantially.

atmospheric pressures until a conversion product dispersible in water at ordinary temperatures is formed. w

.4. The process which consists .in heating starch in the air-dry state to a temperature of about C. without destroying the starch structure, then adding about 2% to about 5% urea,

and continuing the heating to a temperature at which the urea melts and materially decomposes and a starch conversion product is formed which has substantially the original granular structure of the starch and disperses in water at ordinary temperatures without substantial granular disorganization.

5. The process which consists in heating starch with urea under substantially dry conditions and under substantially atmospheric 'pressure at a temperature above the decomposition point of urea, but below about 200 C. until a conversion product dispersible in water at ordinary temperatures is formed. v

6. A cold water-dispersible starchy polysaccharide conversion product which is a reaction product of a starchy polysaccharide with urea, at a temperature at least as high as the decomposition point of urea in the presence of insufiicient moisture and under pressure and temperation point of the urea but under temperature and pressure conditions insufliciently high to destroy the original starch structure.

8. A process of producing a cold water-dispersible starch conversion product which comprises heating tapioca flour containing insufflcient moisture for gelatinization in the presence of urea under'substantially dry conditions at a temperature within the range of about 130 C. to about 200 0., and under pressure conditions insufliciently high to destroy the starch structure until a conversion product is. formed which disperses in water at ordinary temperatures and pressures.

9. A conversion product of a starchy. polysaccharide with urea which po substantially the "structure of the starchy polysaccharide in the dry state and will disperse in water at ordinary temperatures taking up at least six parts of water per part oi conversion product without substantial granular disorganization to produce dispersions which will not vary greatly in consistency with variations in temperature.

.10. A tapioca flour-urea. conversion'product 'which resembles a natural gum in many ofj'its properties and possesses substantially the structure of the natural tapioca flour in the dry state, and which will disperse in six to eight parts of water per part of conversion product at ordinary temperatures without substantial granular diswith temperatures and pressures.

12. A method of producing cold water-dispersible starch conversion products which comprises heating a starchy poiysaccharide which is substantially free from proteins and containing insuflicient moisture for gelatinization in the presence of urea under substantially dry conditions at a temperature within the range of about 130 C. to about 200 C. and at pressures not substantiaily higher than atmospheric until a conversion product is formed which disperses in water at ordinary temperatures and pressures.

GEORGE v. CAESAR. 

